Millions of people around the world have already switched to VoIP. While shopping around for VOIP phone, you will come across lots of terminologies that can be overwhelming and confusing. Following Glossary covers almost all terms and definitions that are commonly used in VoIP technology. Check out latest VoIP terminologies and their meanings.

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VoIP Glossary
Millions of people around the world have already switched to VoIP. While shopping around for VoIP phone,
you will come across lots of terminologies that can be overwhelming and confusing. Following Glossary
covers almost all terms and definitions that are commonly used in VoIP technology. Check out latest VoIP
terminologies and their meanings below.
Analog Telephone Adapter (ATA): A device that connects between an analog telephone and Internet
connection port that allows traditional non-IP phones to work with Voice over IP (VoIP) phone service.
Area Code: Three digit numbers that generally identifies a geographic area of a switch that provides service
to telephone device.
Asymmetric Digital Subscriber Line (ADSL): Technology for bringing high-bandwidth information to homes
and small businesses over ordinary copper telephone lines.
Asynchronous Transfer Mode (ATM): A dedicated-connection switching technology that organizes digital
data into 53-byte cell units and transmits them over a physical medium using digital signal technology. ATM
is designed to take advantage of high-speed transmission media such as E3, SONET, and T3.
Bandwidth: Amount of data that can be passed along a communications channel in a given period of time.
Bandwidth is generally measured in bits per second (bps).
Broadband: It's a term used to define high speed Internet connection, generally provided by cable TV, DSL,
or dedicated telecom lines.
Codec (Compressor/Decompressor): An algorithm used to compress and decompress audio and video files.
Compression: This term is used anywhere from 1:1 to 12:1 ratios in VoIP applications to consume less
bandwidth and leave more for data or other voice/fax communications.
Digital Subscriber Line (DSL): High-speed Internet service via existing copper phone lines or other
channels.
Dual Tone Multi-frequency (DTMF): The type of audio signals generated when you press buttons on a
touch-tone telephone.

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Dynamic Host Configuration Protocol (DHCP): A communications protocol that automatically allocate and
assign IP addresses to multiple devices attached to a network using TCP/IP.
E1: A wide area digital transmission scheme available in Europe that carries data at a rate of 2.048Mbps, as
opposed to a T1 used in North America.
E911 (Enhanced 911): Allows cell phone users to dial 911 and be connected to the closest geographic Public
Safety Answering Point (PSAP).
Ethernet: A popular protocol for broadband bandwidth connectivity over Local Area Networks (LAN).
Firewall: A system designed to block unwanted network traffic going in and out of home or office network.
Fax over Internet Protocol (FoIP): A term to transport facsimiles over Internet.
H.323: An International Telecommunication Union standard call protocol for voice and video conferencing
over LANs, WANs, and Internet
Internet Protocol (IP): A method or protocol that define how data is transmitted over data network.
IP Phone: Also called an Internet phone or broadband phone. IP phone converts voice into digital packets and
vice versa to make phone calls over Internet.
Internet Protocol Telephony (IP Telephony): General term for technologies that uses IP-based data networks
to exchange voice, fax, and other forms of information.
Internet Service Provider (ISP): A company that provides subscriber-based access to Internet.
Internet Telephony Service Provider (ITSP): A company that offers low-cost phone calls that run over
Internet.
Interactive voice response (IVR): A system that collects information from a user to process commands.
Latency: It is the time that elapses between initiation of a request for data and start of actual data transfer.
This delay may be in nanoseconds but it is still used to judge efficiency of networks.

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Multiprotocol Label Switching (MPLS): A method for maximizing network speeds on high traffic networks.
It enables enterprises and service providers to build intelligent networks that deliver scalable, end-to-end
services.
Plain Old Telephone System (POTS): Traditional telephone service over analog lines.
Power over Ethernet (POE): A system to transmit electrical power over a standard twisted pair Ethernet
cable.
Private Branch Exchange (PBX): A private telephone switching system for voice switching and other
telephone related services. PBX routes calls from public telephone system within an organization and allows
direct internal calls.
Public Switched Telephone Network (PSTN): This is an international telephone system that is used in most
of the countries based on copper wires carrying analog voice data.
Router: A device that connects multiple networks together and forwards data packets between them.
Real Time Transport Protocol (RTP): An Internet protocol that functions for end-to-end network connections
for applications that use audio or video.
Session Initiation Protocol (SIP): A communication protocol that operates similarly to H.323 but it's more
Internet and Web-friendly. It's primarily used for Voice over IP calls and is predominant signaling method.
SIP Phone: A SIP phone is a telephone that uses SIP (Session Initiation Protocol) standard to make a voice
call over Internet.
Session Initiation Protocol Trunking (SIP Trunking): It's a Voice over Internet Protocol (VoIP) service
offered by many Internet telephony service providers (ITSPs) that connects a company's private branch
exchange (PBX) telephone system to public switched telephone network (PSTN) via Internet.
SoftPBX: A PBX that is implemented in software, and typically runs on PC. Many softPBXs can be clustered
across multiple machines for reliability and performance.
T1: A 1.544-Mbps point-to-point dedicated digital circuit provided by telephone companies consisting of 24
channels. This is available mainly in the US, as opposed to an E1 that's used in Europe

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T3: An Internet line (also known as a DS-3) is an ultra high-speed connection capable of transmitting data at
rates of up to 44.736 Mbps.
T38: A recognized standard for sending fax transmissions over an IP network in real time mode.
Type of Service (TOS): A method of setting precedence for a particular type of traffic for QoS (Quality of
Service).
User Datagram Protocol (UDP): A communications protocol that offers a limited amount of service when
messages are exchanged between computers in a network that uses Internet Protocol (IP).
Virtual Phone Number: A feature of VoIP that allows attaching additional phone numbers with different area
codes to basic VoIP service.
Virtual Private Network (VPN): It enables IP traffic to travel securely over a public TCP/IP network by
encrypting all traffic from one network to another.
VoIP Phone: A phone that uses Internet to route voice calls by converting voice data into IP packets and vice
versa.
Voice over Internet Protocol (VoIP): A technology that is used to transmit voice over Internet. Also known as
Internet Protocol telephony and IP telephony.
VoIP Gateway: A device, which connects between telephone system and Ethernet network.
Voice over Internet Protocol Private Branch eXchange (VoIP PBX): A telephone switch that converts IP
phone calls into traditional circuit-switched TDM connections. It also supports traditional analog and digital
telephones.
Wi-Fi Phone: A phone that enables users to make phone calls from Wi-FI network environments.
Worldwide Interoperability for Microwave Access (WiMAX): An IP based, wireless broadband access
technology that provides wireless data over long distances in variety of ways, including point-to-point links
and full mobile cellular type access.
Source: http://www.unifiedip.com/voip-glossary/